I keep looking at this picture with a magnifying glass and cannot make up my mind if it is a factory product, or just a one- off homebuilt prototype of some motivated enthusiast's. I keep looking at the details, comparing with all I ever learned as an industrial designer, and still cannot tell which one it could have been.
    Because not only was it so well finished, of so perfect quality, but the frame design itself seemed so appropriate for the job. All design is about compromise. An idea may be ever so grand, but if it's physically difficult to achieve, then it must be adapted to suit the constraints and limitations of the manufacturing (and, in real life also, the marketing and other) process(es). And here I could see directly where those adaptations were made, why the frame utilized an otherwise hard-to- explain combination of bent round tube, and straight square ones. And other such details.
    Unfortunately, I never found out. I kept vigil by the parked bike for well over an hour hoping to meet the rider, but he or she wasn't anywhere near. And then the bike vanished, too. Just as well I have a photo to prove to myself it ever existed.